Various automatic toll collection systems have been proposed to reduce the dependence on a manual attendant for the collection of tolls that the vehicle operator must present at toll collecting locations. It has been known for some time to provide special tokens which the vehicle's operator may deposit at the toll station without manual intervention, with the deposit and subsequent processing of the token providing the vehicle with a signal that it may pass through the toll collecting location. Such a system disadvantageously requires the vehicle's operator to periodically buy a supply of such tokens which are generally only usable at the selling facility. More recently, individually coded electronic transponders are being supplied for mounting to the vehicle. One such system, known as the E-Z PASS is coded to provide an electronic signal unique to a particular vehicle. The vehicle owner obtains the transponder device from the appropriate authority. The transponder is typically mounted on the windshield of the vehicle, and emits a signal which identifies that particular vehicle. As the vehicle approaches the toll station, an antenna located at the toll station ascertains the presence of the vehicle and will debit the appropriate toll to the vehicle's operator's account which has been established at the time the vehicle operator obtains the vehicle-mounted transponder from the toll collection authority. The balance of the vehicle operator's account may either be periodically replenished by electronic deposit, the forwarding of check drafts to the toll collection authority, or periodic debiting to the vehicle operator's general charge account. This toll collection system advantageously simplifies the process of collecting tolls, speeds up traffic flow through the toll station, and reduces the cost of collecting tolls by dispensing with the need to have an attendant at the toll station to make the currency exchange with the vehicle's operator. However, because of the continued presence of the transponder in an activated mode within the vehicle, there may be situations when the vehicle operator prefers not to emit the signal. For example, the operator may want to pay a particular toll with currency rather than have it automatically debited to the account set up in association with the transponder. Further the ability to ascertain the identification of the transponder at a location other than the toll station could subject the transponder to improper cloning, or be the basis for privacy concerns. Accordingly, it would be preferable to limit the activation of the transponder to those situations in which the vehicle operator is passing is through the toll station and desires to utilize the transponder for the automatic toll collection.